Flash cards
Review the key moves
1/4
Core idea
What is the main idea behind Java Identifiers?
Lesson checks
Practice each idea before moving on
Short Mimo-style checks built from this lesson's code, terms, and sequence.
1Quick choice
Which statement best captures the main point of this lesson?
2Fill blank
Complete the missing token from the example code.
// ___ int minutesPerHour = 60;3Order
Put the learning moves in the order that makes the concept easiest to apply.
These unique names are called identifiers .
All Java variables must be identified with unique names .
Invalid Identifiers
Identifiers
All Java variables must be identified with unique names .
These unique names are called identifiers .
Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume).
Note
It is recommended to use descriptive names in order to create understandable and maintainable code:
// Good int minutesPerHour = 60;
// OK, but not so easy to understand what m actually is int m = 60;The general rules for naming variables are:
- Names can contain letters, digits, underscores, and dollar signs
- Names must begin with a letter
- Names should start with a lowercase letter, and cannot contain whitespace
- Names can also begin with $ and _
- Names are case-sensitive ("myVar" and "myvar" are different variables)
- Reserved words (like Java keywords, such as int or boolean ) cannot be used as names
Invalid Identifiers
Here are some examples of invalid identifiers that would cause errors:
Example
// Invalid identifiers: int 2ndNumber = 5; // Cannot start with a digit int my var = 10; // Cannot contain spaces int int = 20; // Cannot use reserved keywords